The objective of this proposal is to investigate the hormonal requirements for the development of ovarian and testicular tumors in inhibin-deficient mice and the cachexia that is associated with the progression of these tumors. Using the inhibin-deficient mouse model developed by the investigator, the following studies are proposed. Aim 1 will examine the individual roles of FSH and LH in tumor development and progression in inhibin-deficient mice. Aim 2 will characterize the requirements for gonadal steroids in the development and progression of tumors in the inhibin-deficient mice. Aim 3 will determine if overexpression of follistatin can prevent the activin-mediated cachexia-like syndrome that occurs in the inhibin-deficient mice. Aim 4 will define the pattern of expression/extinction of cell cycle regulatory molecules that accompanies tumor development and growth.